in chapter 4, in Concept Question number 3 (http://ocw.mit.edu/courses/physics/8-01sc-physics-i-classical-mechanics-fall-2010/translational-kinematics/one-dimensional-kinematics-and-free-fall/MIT8_01SC_quiz04_sols.pdf)
why graph 3 is not a right option either?
thank you !

Question

in chapter 4, in Concept Question number 3 (http://ocw.mit.edu/courses/physics/8-01sc-physics-i-classical-mechanics-fall-2010/translational-kinematics/one-dimensional-kinematics-and-free-fall/MIT8_01SC_quiz04_sols.pdf) 
why graph 3 is not a right option either? 
thank you !

waynex · Answer

In graph 3 the curve has downward curvature and means x is growing (negative growth) faster with larger t.